Method and system for automatically inspecting ophthalmic lenses

• US 5,748,300 A
• Filed: 09/12/1996
• Issued: 05/05/1998
• Est. Priority Date: 12/21/1992
• Status: Expired due to Term

• Current Assignee: Johnson & Johnson Vision Products, Inc.
• Original Assignee: Johnson & Johnson Vision Products, Inc.
• Inventors: Wilder, Joseph, Dreyfuss, David
• Primary Examiner(s): Pham, Hoa Q.
• Application Number:
  US08/712,245
• Time in Patent Office: 600 Days
• Field of Search: 356/124-127, 356/237, 356/239, 356/240, 356/430, 356/244, 356/246, 264/2.6, 250/562, 250/572, 250/223 B, 358/101, 358/106, 358/107, 382/8, 382/65
• US Class Current: 356/124
• CPC Class Codes: G01M 11/0214 Details of devices holding the object to be tested
• CPC Class Codes: G01M 11/0221 by determining the optical axis or position of lenses
• CPC Class Codes: G01M 11/0235 by measuring multiple properties of lenses, automatic lens meters
• CPC Class Codes: G01M 11/0278 Detecting defects of the object to be tested, e.g. scratches or dust investigating the presence of flaws or contamination on materials by optical means G01N21/88

Abstract

A method and system for automatically inspecting an ophthalmic lens. The method includes the steps of directing a light beam through the lens and onto an array of pixels, and assigning to each pixel a data value representing the intensity of the light beam on the pixel. The data values are then processed according to a predetermined program to determine if the lens contains any one of a group of predetermined conditions.

Claims

1. A method for automatically inspecting an ophthalmic lens which includes an annular edge portion having generally circumferential inner and outer edges, comprising:

directing a light beam through the lens and onto an array of pixels to form images thereon of the inner and outer edges of the annular edge portion;

assigning to each pixel a data value representing the intensity of the light beam on the pixel; and

processing said data values according to a predetermined program to determine if the lens contains any one or more of a plurality of predetermined conditions;

wherein the processing step includes the steps of

i) identifying a center point on the pixel array and a radius of a first circle having a circumference generally commensurate with the image of the outer edge of the annular edge portion,

ii) identifying a center point on the pixel array and a radius of a second circle having a circumference generally commensurate with the image of the inner edge of the annular edge portion,

iii) determining a distance between the center points of the first and second circles,

iv) comparing said distance to a predetermined distance value, and

v) identifying the lens as being decentered if said distance is greater than said predetermined distance value.

2. A method according to claim 1, wherein:

the step of identifying the center point and the radius of the first circle includes the steps of

i) identifying at least three first pixels on the image or the outer edge of the annular edge portion, and

ii) identifying a center point and a radius of a circle having a circumference passing through said three first pixels, and

the step of identifying the center point and the radius of the second circle includes the steps of

i) identifying at least three second pixels on the image of the inner edge of the annular edge portion, and

ii) identifying a center point and a radius of a circle having a circumference passing through said three second pixels.

3. A method according to claim 2, wherein:

the steps of identifying the three first pixels and the three second pixels include the steps of

identifying a multitude of series of pixels, each of said pixels forming a line segment; and

checking each said series of pixels for transitions between pixels illuminated above and below a given intensity level.

4. A method according to claim 3, wherein the step of identifying a multitude of series of pixels includes the steps of

for each said series,

identifying a starting point for the series,

identifying a direction for the series, and

identifying a length for the series.

5. A method according to claim 1, wherein

the processing step includes the steps of

i) identifying at least selected ones of the pixels located on the image of the outer edge of the lens, and

ii) identifying gaps and extra pieces on the image of the outer edge of the lens,

iii) for each identified gap, determining a width of the gap, comparing said width to a predetermined width value and identifying the lens as flawed if said width is greater than said predetermined width value,

iv) for each identified extra piece on the image of the outer edge of the lens, determining an area of the extra piece, comparing said area to a predetermined area value and identifying the lens as flawed if said area is greater than said predetermined area value.

6. A method according to claim 5, wherein the step of identifying gaps and extra pieces on the image of the outside edge of the lens includes the steps of

identifying a center point on the pixel array and a radius of a first circle having a circumference generally commensurate with the image of the outside edge of the lens;

for each of said selected ones of the pixels, determining a distance between said pixel and said circumference,

identifying the lens as having a gap if, for each of a given number of consecutive pixels on the outside edge of the lens image, the pixel is radially inside said circumference and the distance between the pixel and said circumference is greater than a given distance; and

identifying the lens as having an extra piece if, for each of a given number of consecutive pixels on the outside edge of the lens image, the pixel is radially outside said circumference and the distance between the pixel and said circumference is greater than a selected distance.

7. A method according to claim 6, wherein the step of determining the width of the gap includes the step of, once a gap has been identified, searching for an end of the gap by searching across the gap, along said circumference of the first circle, and searching radially inward and outward from said circumference, for one of the pixels on the outer edge of the lens image.

8. A method according to claim 1, wherein:

the assigning step includes the step of assigning to each pixel a digital data value; and

the processing step includes the steps of

i) processing said digital data values, using at least one algorithm, to produce a set of digital values, and

ii) using said set of digital values to determine if the lens contains any of said predetermined conditions.

9. A method according to claim 8, wherein:

the lens has an edge;

the step of processing said digital values includes the step of processing said digital data values using an edge detection algorithm; and

the using step includes the step of using said set of digital values to identify pixels on the edge of the lens.

10. A method for automatically inspecting an ophthalmic lens which has an outside edges, comprising:

directing a light beam through the lens and onto an array of pixels to form an image thereon of the outside edge of the lens;

assigning to each pixel a data value representing the intensity of the light beam on the pixel; and

processing said data values according to a predetermined program to determine if the lens contains any one or more of a plurality of predetermined conditions;

wherein the processing step includes the steps of

i) identifying at least selected ones of the pixels located on the image of the outside edge of the lens,

ii) identifying gaps on the image of the outside edge of the lens,

iii) emphasizing each identified gap by assigning high data values to selected pixels in or adjacent the gap.

11. A method according to claim 10, wherein the emphasizing step includes the steps of:

for each identified gap,

identifying a first pixel as a beginning of the gap,

identifying a second pixel as an end of the gap, and

assigning high data values to the pixels on a line segment between said first and second pixels.

12. A method according to claim 11, wherein the emphasizing step further includes the step of also assigning high data values to the pixels in the gap in the image of the outside edge of the lens.

13. A method for automatically inspecting an ophthalmic lens which has a generally circumferential outside edges, comprising:

directing a light beam through the lens and onto an array of pixels to form an image thereon of the outside edge of the lens;

assigning to each pixel a data value representing the intensity of the light beam on the pixel; and

processing said data values according to a predetermined program to determine if the lens contains any one or more of a plurality of predetermined conditions;

wherein the processing step includes the steps of

i) identifying a center point on the pixel array of a circle having a circumference generally commensurate with the image of the outside edge of the lens,

ii) identifying at least selected ones of the pixels located on the image of the outside edge of the lens,

iii) for each of the selected ones of the pixels, identifying another pixel on the outside edge of the lens image, a given distance from said selected one of the pixels,

identifying a first vector extending through said selected one of the pixels and said another pixel,

identifying a second vector extending through said selected one of the pixels and said center point,

computing a dot product of said first and second vectors, comparing the dot product to a predetermined product value, and identifying the lens as flawed if the dot product is greater than said predetermined product value.

14. A method for automatically inspecting an ophthalmic lens which has an outside edges, comprising:

directing a light beam through the lens and onto an array of pixels to form an image thereon of the outside edge of the lens;

assigning to each pixel a data value representing the intensity of the light beam on the pixel; and

processing said data values according to a predetermined program to determine if the lens contains any one or more of a plurality of predetermined conditions;

wherein the processing step includes the steps of

i) identifying at least selected ones of the pixels located on the image of the outside edge of the lens,

ii) identifying extra pieces on the outside edge of the lens image, and

iii) emphasizing each identified extra piece by assigning high data values to selected pixels adjacent the extra piece.

15. A method according to claim 14, wherein the emphasizing step includes the steps of:

for each identified extra piece,

identifying a first pixel as a beginning of the extra piece,

identifying a second pixel as an end of the extra piece, and

assigning high data values to the pixels on a line segment between said first and second pixels.

16. A method according to claim 15, wherein the emphasizing step further includes the step of assigning high data values to the pixels on the extra piece.

17. A method according to claim 14, wherein the emphasizing step includes the steps of:

for each identified extra piece,

identifying a first pixel on a front side of the extra piece,

identifying a second pixel on the edge of the lens image forward of the extra piece and a given distance from said first pixel,

identifying a third pixel on a back side of the extra piece,

identifying a fourth pixel on the edge of the lens image, rearward of the extra piece and a selected distance from the third pixel,

assigning high data values to the pixels on a first line segment between said first and second pixels, and assigning high data values to the pixels on a second line segment between said third and fourth pixels.

18. A method according to claim 17, wherein:

the extra piece, the outside edge of the lens image and the first line segment bound a first area containing a first group of pixels;

the extra piece, the outside edge of the lens image and the second line segment bound a second area containing a second group of pixels; and

the emphasizing step further includes the step of assigning high data values to the first and second groups of pixels.

19. A method for automatically inspecting an ophthalmic lens which has an outside edges, comprising:

directing a light beam through the lens and onto an array of pixels to form an image thereon of the lens showing the outside edge thereof;

assigning to each pixel a data value representing the intensity of the light beam on the pixel; and

processing said data values according to a predetermined program to determine if the lens contains any one or more of a plurality of predetermined conditions;

wherein the processing step includes the steps of

identifying selected areas of the pixel array having pixels having high data values; and

emphasizing said selected areas by assigning high data values to pixels adjacent said selected areas,

identifying the pixels on the outside edge of the lens image, and

assigning low data values to the pixels on the outside edge of the lens image.

20. A method according to claim 19, wherein the processing step further includes the step of searching for groups of contiguous pixels having high data values.

21. A system for automatically inspecting an ophthalmic lens which includes an annular edge portion having generally circumferential inner and outer edges, comprising:

an array of pixels;

means to direct a light beam through the lens and onto the array of pixels, the means to direct the light beam includes means to form on the pixel array images of the inner and outer edges of the annular edge portion;

means to assign to each pixel a data value representing the intensity of the light beam on the pixel; and

processing means to process said data values according to a predetermined program to determine if the lens contains any one or more of a plurality of predetermined conditions;

wherein the processing means includes

i) means to identify a center point on the pixel array of a first circle having a circumference generally commensurate with the image of the outer edge of the annular edge portion,

ii) means to identify a center point on the pixel array of a second circle having a circumference generally commensurate with the image of the inner edge of the annular edge portion,

iii) means to determine a distance between the center points of the first and second circles, and

iv) means to identify the discs of the lens as being decentered if said distance is greater than a predetermined value.

22. A system according to claim 21, wherein

the processing means further includes

i) means to identify gaps and extra pieces on the image of the outer edge of the lens,

ii) means to determine a width of each identified gap, and to identify the lens as flawed if said width is greater than a predetermined width value, and

iii) means to determine a size of each identified extra piece, and to identify the extra piece as flawed if said size is greater than a preselected size value.

23. A system according to claim 22, wherein the processing means includes means to emphasize each gap and each extra piece by assigning high data values to pixel adjacent the gaps and the extra pieces.

24. A system according to claim 21, wherein the processing means further includes

means to identify selected areas of the pixel array having pixels with high data values, and

means to emphasize said selected areas by assigning high data values to pixels adjacent said selected areas.

25. A system according to claim 24, wherein the lens has an outside edge, and wherein:

the means to direct the light beam includes means to form on the pixel array an image of the outside edge of the lens; and

the processing means further includes

i) means to identify pixels on the outside edge of the lens image, and

ii) means to assign low data values to the pixels on the outside edge of the lens image.

26. A system according to claim 25, wherein the processing means further includes means to search for groups of contiguous pixels having high data values.

27. A system according to claim 21, wherein:

the means to assign includes means to assign to each pixel a digital data value; and

the processing mean includes a processor using at least one algorithm to produce a set of digital values, and using said set of digital values to determine if the lens contains any of said predetermined conditions.

28. A system according to claim 27, whereas:

the lens has an edge; and

the processor process said set of digital values to identify pixels on the edge of the lens.

29. A system for automatically inspecting an ophthalmic lens which has a generally circumferential outside edge, comprising:

an array of pixels;

means to direct a light beam through the lens and onto the array of pixels, the means to direct the light beam includes means to form in the pixel array an image of the outside edge of the lens;

means to assign to each pixel a data value representing the intensity of the light beam on the pixel; and

processing means to process said data values according to a predetermined program to determine if the lens contains any one or more of a plurality of predetermined conditions;

wherein the processing means includes

i) means to identify a center point on the pixel array of a circle having a circumference generally commensurate with the image of the outer edge of the lens,

ii) means to identify at least selected ones of the pixels located on the image of the outer edge of the lens,

iii) means to identify, for each one of the selected pixels, another pixel on the outer edge of the lens image, a given distance from said selected one of the pixels; and

to identify a first vector extending through said selected one of the pixels and said another pixel, and to identify a second vector extending through said selected one of the pixels and said center point, and

iv) means to identify the lens as flawed if a dot product of said first and second vectors is greater than a predetermined value.

30. A method for automatically inspecting an ophthalmic lens, comprising the steps of:

directing a light beam through the lens and onto an array of pixels;

assigning to each pixel a data value representing the intensity of the light beam on the pixel; and

processing said data values according to a predetermined program to determine if the lens contains any one of a plurality of predetermined condition, the processing step including;

identifying the lens as being decentered if a center of an inner circle having a periphery at an inner edge of an annular edge portion of the lens is away from a center of an outer circle having a periphery at an outer edge of the annular edge portion by a predetermined distance; and

p2 discarding data located outside the outer circle.

31. The method of claim 30, wherein the identifying step includes the steps of:

searching inward from an edge of the array of pixels until an illuminated pixel is found;

comparing a distance from said found pixel to the center of the outer circle to a radius of the outer circle; and

discarding said found illuminated pixel if said distance is different from said radius by a predetermined value.

32. The method of claim 30, wherein the identifying step includes identifying at least three first pixels on each of the outer and inner circles.

33. The method of claim 30, wherein the discarding step retrieves coordinates of the center of the outer circle, and discards data located outside a circle having a center equal to the retrieved center, and a radius which is slightly larger than a radius of the outer circle.

34. The method of claim 30 further comprising the steps of:

determining whether a gap or extra piece is present in the processed data; and

rejecting the lens if a widths of a gap or extra piece found in the determining step exceed a predetermined value.

35. The method of claim 30 further comprising emphasizing defects found in the lens by assigning one of high and low values to pixels in or adjacent said defects.

36. The method of claim 30 further comprising the steps of:

determining a tangent vector to a pixel located on said outer circle;

determining a radial vector to said pixel located on said outer circle;

computing a dot product of said tangent and radial vectors; and

identifying the lens as flawed if the dot product is greater than a predetermined value.